Dedicated printers, copiers and facsimile machines all have multiple sheet printing capabilities requiring a feeder mechanism which inserts sheets into a media feed path. The recent trend has been for suppliers of such equipment to combine multiple functions in a single device. For example, digital printing devices are now available that can function as either a copier or as a printer. Other digital printing devices combine printing, copying, facsimile and scanning functions. Each such printing device generally has at least one of what is known in the industry as a page stop location. A page stop location is the furthest position to which a new page may be inserted into a media path without that page interfering with the movement of other media sheets already in the path, or with moving mechanical components within the device. The stop location can apply to media sheets being fed into an internal media path, or to media sheets being fed from the media transport path of one device to the media transport path of another device. A new page must not pass the stop location until the printing device is ready to receive it. Stop locations are usually stated as a distance from the media path entrance. For devices which are externally attachable to a host device, the path entrance is generally located on a face of the attachable device, a face which generally mounts flush with a receiving face of the host device.
The page stop value of a device is a critical factor as pages are fed into its media path entrance. If, for example, the actual page stop location is 28.4 mm, a media jam will occur if the media page is stopped beyond that value at, say, 28.5 mm. Because of certain variables, such as thermal expansion and mechanical tolerances, a page stop specification is generally given as an optimum distance value with a tolerance. Even in the case where the tolerance is at the high-side maximum, the value still provides at least some leeway against a jam condition. For an actual page stop location of 28.4 mm, the page stop specification might be given as 26.4 mm.+-.1.0 mm. Thus, even if a newly-fed page stops at 27.4 mm (the high-side tolerance), the page is still 1.0 mm from causing a jam condition.
Heretofore, the parking of media sheets just short of a stop location has been empirically determined by estimating how long it will take for the sheet to travel from an identifiable starting point along the media path to the stop location. A timer, set to the estimated time, begins a countdown to zero as a media page passes a sensor identifying the starting point. Movement of the page along the media path is stopped when the timer expires, and the page is checked for proper positioning at the stop location. The process is repeated until the time for proper positioning to be achieved is accurately known.
The integration of a printing device with one or more attached devices, such as media input handlers, collators, binders, mailers or duplexing attachments, is time consuming because each device which feeds media sheets to another device must know the stop location of the receiving device in order to prevent media jams when a media sheet is transferred from the feed device to the receiving device.
What is needed is a method for automatically calibrating media feed timing for the stop locations of interconnected devices so that development and integration of multiple device systems is no longer a cumbersome, time-consuming task.